The surfaces of freshly slaughtered and eviscerated poultry and other meats are contaminated with microorganisms that are present on the animals' skins, hides, feathers and hair from fecal contact from both the animal itself and nearby animals, as well as by physical transfer from the animals' viscera through contact with processing equipment. The bacteria of greatest concern are pathogens such as Salmonella and Campylobacter species, Escherichia coli, including the particularly virulent strain 0157:H7, Listeria monocytogenes and other harmful enterobacteriaceae. Many of these organisms can survive carcass scalding temperatures of 50.degree. C. to 58.degree. C., and thereafter cross-contaminate other carcasses on the processing line. This is true also for the so-called "spoilage organisms," where excessive levels of the psychrotrophic and lactic acid bacteria will reduce the shelf-life of the final processed poultry and meat products by proliferating to a level where odor and textural qualities make the meat products unacceptable to the consumer.
In poultry processing, until recently, the primary focus for reducing surface pathogens was directed to the use of chiller tanks, where antimicrobials such as chlorine and chlorine dioxide were included in the processing waters. These were intended to lower the levels of carcass pathogens that had transferred to the water, and reduce their cross-contamination with other carcasses. Regulatory authorities in the United States have now approved the use of acidified chlorite/chlorous acid antimicrobial systems for inclusion in chiller tanks, as well as for direct application to the defeathered/eviscerated carcasses immediately prior to their immersion in the chiller waters. This results in the destruction of surface pathogens on individual carcasscs, thereby reducing or eliminating their numbers so that they cannot subsequently contaminate the chiller waters and other non-contaminated carcasses. The application of these chlorite/chlorous acid systems may be either by separate immersion of each poultry carcass in the liquid germicide solution, or by spray application. When these systems are used to disinfect the surfaces of red-meat carcasses, following evisceration, they are applied as sprays.
The chlorite/chlorous acid technology was the subject of U.S. Pat. No. 5,389,390, for removing bacteria from poultry and other meats. According to that patent, the disinfecting solutions can contain about from 0.001% to about 0.2% by weight of metal chlorite, with a sufficient quantity of acid to adjust the pH of the solution to about 2.2 to about 4.5 (and to maintain the chlorite ion concentration in the form of chlorous acid to not more than about 35% by weight of the total chlorite ion present in the aqueous solution). Under such conditions no more than about 35% by weight of the total chlorite ion (C10.sub.2.sup.-) that is present will exist in the chlorous acid (HC10.sub.2) form. Preferred acids may be strong inorganic acids such as sulfuric, hydrochloric or phosphoric, or moderate-strength organic acids such as citric, malic or fumaric.
It has now been found that when such chlorite/chlorous acid solutions are applied as sprays to red-meat and poultry carcass surfaces, the levels of disinfection that are achieved are significantly lower than those achieved by immersion. Thus, there is a continuing need for an effective and safe spray disinfectant to apply to animal carcasses soon after the evisceration process, before contaminating organisms can develop a firm foothold on the meat surfaces. The present invention fulfills these needs and provides further related advantages.